This is probably a dumb question, but my Chromacolor 2 has a buzzing in the audio when on screen grapics come on. Like when I'm watching the news, or when a commercial comes on. It's really bad on DVD's. Which control needs adjusted, or what module do I need to be looking at. I tried backing off the AGC a bit, but it didn't help.

Try replacing the IF board (it's probably an alignment problem). Also, try turning off the AFC and manually fine tuning it. If you can get rid of the buzzing and still have a good picture, try adjusting the AFT coil on the IF board.

The 150-190 board? I tried adjusting the AFC and it made no differeance. And here's the kicker.... it only does it once in awhile. It was bad last night, and is not doing it this morning. This set has been eating up modules as of late. Last month the vertical went nuts, so I replaced the 9-147. Fixed that problem. A few weeks later the screen would flash red, so replaced the video module. Fixed that problem. Now this. This set is my daily watcher, and when working has a better picture than my new Toshiba. However, it sure has been glitchy lately, which is odd for a Zenith. But hell.... it IS 31 years old now. Was probably a high hour set when I got it, and I have it on every day. I bet the Toshiba won't be on in 31 years.

I agree with Andy... Most of the circuitry that can cause a buzz should be in that IF pack. However, I think I recall some of the audio IF being on the small audio module, which has 2 or 3 adjustable transformers on it. I never had to fool with those, as I just replaced the module if there was trouble.

I am going to guess that you're hearing video leaking into the audio, possibly a VIR signal (same thing that causes the hated retrace lines at the top of the picture on some channels that use the VIR bandwidth).

So the IF and audio modules would be the first things to try. I probably have those modules, so if you can't find one locally you can eMail me at [email protected] (I seldom check AK messages, so eMail is always best)

Charles

If you're on cable, some channels might have slightly over-modulated video. That's not a problem for a modern set, but an old IF circuit that's not perfectly aligned will cause some leakage into the sound.

As for your set eating modules, bad soldering is the most common problem with those. Zenith never really got the hang of circuit board soldering, even by the late 80's they were still having trouble. It's also not unusual to see old TVs with numerous intermittent problems that the original owner put up with. Once you fix the main problem with the set, those other problems gradually become apparent.

One of my friends has a very new 32" set that does this. It's a silver box, I want to say Phillips, but I don't remember - and the buzz seems to come along with the bright scenes - and the more white in the image, the more buzz. You don't hear the buzz at all most of the time, but as soon as the scene changes to something bright, it buzzes. It's weird. We always just assumed it was haunted.

-Ian

I am not familiar with the solid state sets, but have seen many a tube set with buzz in the audio. These sets used the ratio detector and the quadrature detector which are required to be in very good shape and aligned very well to reject the amplitude modulation in the video.

I have a couple of B&W sets with the Armstrong limiter/discriminator setup. I have not restored these yet, but am very curious as to how these will work in a TV. Suprsingly, considering the fighting between Sarnoff and Armstrong, these sets are 1950s RCA sets. I have several Zenith radios from the 1950s and the limiter/discriminator setup works very well in these.

Suprsingly, considering the fighting between Sarnoff and Armstrong


You mean when Sarnoff murdered Armstrong after stealing with malice and forethought all of his intelligence, and preying upon his kindness and selflessness (forced him to suicide).....

Just a little historical political rant :nono:

Charles

I have several Zenith radios from the 1950s and the limiter/discriminator setup works very well in these.

I have always found the FM performance of Zenith radios to be better than that of RCA. The zeniths are easier to tune, don't drift and the stations don't bleed into one another as they did on two RCAs I used to have.

I also like the Zenith FM sets. As the early 1950s ones do not have AFC, they do drift to varying degrees as they warm up. Most Zeniths used the 12AT7 tube as the FM oscillator and converter tube. I have other sets(including some cheaper Zeniths) that used the 12BE6 in this role. The performance of these sets has not been as good as the ones that use the 12AT7.

The main issue I had with Zeniths and other 1950s radios is the IF capacitor corrosion issue. There are instructions on the internet on how to fix this.